1. Field of the Invention
The invention relates to a driving switching system applied to motors and a method thereof, and more particularly to the driving switching system and method for motors that can base on the first kickback voltage and the second kickback voltage to determine the switching among various MOSFETs to drive the motor from a first current phase to a second current phase, as preset threshold voltages are reached.
2. Description of the Prior Art
The motor is one of the popular mechanic parts in normal life. In the driving circuit of the conventional motor, the H-bridge circuit and the driving module are two important elements. Generally, the H-bridge circuit includes two P-type Metal-Oxide-Semiconductor Field-Effect Transistors (PMOSFETs) and two N-type Metal-Oxide-Semiconductor Field-Effect Transistors (NMOSFETs). In structuring, a pair of one PMOSFET and one NMOSFET in series is electrically coupled with another pair of PMOSFET and NMOSFET in series through a coil, in which the two PMOSFETs are electrically connected to the source power VDD, while the two NMOSFET are electrically connected to the ground VSS. The driving module is electrically connected the aforesaid two PMOSFETs and the aforesaid two NMOSFETs.
In the art, the H-bridge circuit is to drive the motor. As the H-bridge circuit drives the motor, it may meet a situation that the current is terminated during the commutation of the motor; such that kickback voltages would be generated at either end or both ends of the coil (where the PMOSFET and the NMOSFET are electrically connected). Sometimes, the kickback voltage may be higher than the source power VDD or lower than the ground VSS. As an ill consequence, the aforesaid PMOSFETs and NMOSFETs may be damaged, and further the motor may be degraded or even shutdown.
Further, for the nature of the PMOSFET and the NMOSFET, the parasitic diodes may extend the tolerance of the kickback voltage (for example, from VDD+Vd to VSS−Vd). However, in practice, the formation of the kickback voltage usually interferes the driving of the motor or leads to the damage of the IC through the CMOS latch-up phenomenon.
It is clear that the kickback voltage would damage the PMOSFET and the NMOSFET in the motor's driving circuit, and would dysfunction the motor to some degree. Further, the induced latch-up effect would also damage the IC. Hence, it is definitely welcome to the art to an effort in improving the motor's driving circuit to act against the kickback voltage.